Degreasing process

ABSTRACT

The invention is a process for degreasing animal skins in which the animal skin to be degreased is contacted with a mixture of a predominantly saturated C 12  -C 18  fatty alcohol ethoxylate having an average of not more than 15 EO groups and a predominantly saturated C 6-10  fatty alcohol ethoxylate having an average of not more than 3 EO groups.

This application is a 371 of PCT/EP93/00527 filed Mar. 9, 1993.

FIELD OF THE INVENTION

This invention relates to degreasing preparations based on nonionicemulsifiers of the fatty alcohol ethoxylate type for the treatment ofskins, pelts, hides, leathers and the like.

RELATED ART

In the production of leathers and furs, the use of nonionic surfactantsor surfactant mixtures and solutions thereof in selected auxiliaryliquids, more particularly organic solvents, is of considerableimportance in a number of process steps where products belonging to theclasses in question are used. Compounds of this type are used inparticular in the degreasing of pelts, for example in the treatment ofsheepskins, and quite generally for surface degreasing or thoroughcleaning in the soaking, liming and bating steps and also in other stepsinvolved in the manufacture of leathers and furs.

Known nonionic emulsifiers of the type in question are additioncompounds of ethylene oxide and/or propylene oxide with alkylphenols,fatty alcohols or fatty acids. The importance of the class of compoundsin question lies inter alia in the fact that nonionic emulsifiers of thedescribed type have hardly any capacity for attachment to the skin orleather fibers. Accordingly, they are able optimally to perform theirfunction of solubilizing sebum without being impeded by interaction withthe skin itself.

One of the hitherto most commonly used compounds of this class ofsurfactants belongs to the group of alkylphenol ethoxylates. Thecompound in question is nonylphenol ethoxylate which contains an averageof 10 EO groups and which is marketed under a variety of names for theparticular application in question. The desired result in regard to thedegreasing of skins and/or pelts is optimally achieved. Nevertheless,there is concern about the continued use of this compound. Itsdegradation products can lead to problems in biological stages of sewagetreatment plants.

Experts have for some time developed comparable products based on fattyalcohol alkoxylates which are capable of at least partly fulfilling therequired performance profile, but are less problematical in terms ofwastewater treatment than the aromatic alkyl compounds mentioned above.

Thus, German patent application DE-OS 25 22 902 describes degreasingpreparations containing nonionic and/or anionic surfactants asauxiliaries. Example 1 specifically discloses a mixture containing 10%by weight of an anionic surfactant (alkyl benzenesulfonate), 10% byweight of alcohol-based solvent (isopropyl alcohol), 20% by weight of anadduct of 10 moles of ethylene oxide with C_(12/18) fatty alcohol and20% by weight of an adduct of 3 moles of ethylene oxide with C_(10/12)fatty alcohol. However, a degreasing process based on a mixture such asthis could never be satisfactory on account of the large number ofauxiliaries required. In addition, increasing environmental awarenessdictates that the use of anionic surfactants and the use of solventsshould be avoided as far as possible.

BRIEF DESCRIPTION OF THE INVENTION

However, the requirement profile which the degreasing preparationsaccording to the invention are expected to satisfy is not confined totheir outstanding capacity for emulsifying and dispersing fats, fattyacids, metal soaps and/or waxes and soil residues of all kinds; on thecontrary, there are a number of other requirements to be satisfied. Thedegreasing preparations should be readily removable from the skin bywashing and should not enter into any unwanted interactions with otheranionic, cationic and/or nonionic substances, for example dyes and fatliquors. They should also show adequate electrolyte stability and, inparticular, should be unaffected by water hardness, more particularly byhigh degrees of water hardness. Finally, the degreasing preparationsshould be usable both at acidic and at alkaline pH values.

Accordingly, the problem addressed by the present invention was toprovide an optimized degreasing preparation based on nonionic fattyalcohol alkoxylates which would be widely usable under variousconditions with optimal results.

According to the invention, the solution to this problem lies in thespecific choice and blending of various active-substance componentswhich, overall, may be assigned in terms of constitution to a class ofcompounds showing optimal biological compatibility.

Accordingly, the present invention relates to degreasing preparationsbased on nonionic emulsifiers of the fatty alcohol alkoxylate type forthe treatment of skins, pelts, hides, leathers and the like, containinga mixture of

(a) C₁₂₋₁₈ fatty alcohol ethoxylates containing on average more than 6EO groups in the molecule and

(b) head-fractionated fatty alcohol ethoxylates containing no more than3 EO groups in the molecule, with the proviso that

i) the fatty alcohols on which components (a) and (b) are based have aniodine value below 20 and

ii) component (b) is present in a quantity of about 2 to 20% by weight,based on the sum of (a) and (b).

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the core of the teaching according to the invention lies inthe combined use of selected medium- to long-chain fatty alcoholethoxylates--class (a) compounds--and nonionic EO compounds--class (b)compounds--which are derived from so-called head-fractionated fattyalcohols.

It is known that so-called head-fractionated fatty alcohols arepreferably linear representatives of the <C₁₂ range and, moreparticularly, the range from around C₆ to C₁₀. According to theinvention, particular significance is attributed to the C₈head-fractionated fatty alcohol and/or mixtures thereof with C₁₀head-fractionated fatty alcohols.

According to the invention, ethoxylates of alcohols with carbon chainlengths in the ranges mentioned and with an iodine value below 20 areused both in the compounds of class (a) and in compounds of class (b).The choice of the method used to determine the iodine value is of minorimportance. For the purposes of the present invention, however,reference is specifically made to the methods of Hanus-and Wijs, whichhave long been part of section C-V of the "DGF-Einheitsmethoden", and toFiebig's more recent equivalent method (cf. Fat Sci. Technol. 1991, No.1, pages 13-19).

A particularly preferred embodiment of the invention is characterized bythe use of representatives of classes (a) and (b) where the iodine valueof the basic fatty alcohol is below 5 and, more particularly, below 3.The feature of the iodine value is intended to illustrate the fact thatthe teaching according to the invention is directed to mixtures ofrepresentatives of classes (a) and (b) where the basic fatty alcoholsare predominantly saturated.

Among the alcohols on which components (a) and (b) are based, particularsignificance is attributed to those of natural origin. It is known thatthe corresponding alcohols of vegetable and/or animal origin can beobtained from the associated fatty acids of vegetable and/or animalorigin by hydrogenation. The alcohols in question are at least by farpredominantly alcohols or alcohol mixtures with an even number of carbonatoms. Accordingly, ethoxylates of the corresponding linear, saturatedC₁₂, C₁₄, C₁₆ and C₁₈ alcohols are particularly suitable for use ascomponent (a). Mixtures of these types of alcohols are preferred asparent substances for the ethoxylates (a). The most important alcoholcomponent of the class (b) compounds is head-fractionated C₈ fattyalcohol.

Component (a) selected as an effective fat emulsifier makes up thelarger part of the degreasing preparation according to the inventionbased on the mixture of (a) and (b). The smaller part made up bycomponent (b) amounts to between 2 and 25% by weight, based on the sumof (a) and (b). The range from 5 to 22% by weight is particularlypreferred.

According to the invention, component (b) performs an importantfunction, more particularly as a dispersion aid which facilitates theuptake and emulsification of fats, waxes and the like by the mainactive-substance components of the class (a) compounds according to theinvention. The combined use of predominant quantities of the emulsifiers(a) and small quantities of the dispersants (b) is crucial to theimproved result achieved in accordance with the invention.

In one preferred embodiment, the achievement of these objectives isfurther assisted by a certain choice of components (a). In thisembodiment of the invention, mixtures of fatty alcohol ethoxylatesdiffering in their average EO degrees are used as component (a). Therange of on average up to 15 EO units per molecule of the fatty alcoholis preferably not exceeded.

In one important embodiment, mixtures of the following subclasses (a1)and (a2) are used in the class of components (a):

(a1): saturated C₁₂₋₁₈ fatty alcohol ethoxylates with an average EOdegree of 6 to 10 and more particularly 6 to 8

(a2): C₁₂₋₁₈ fatty alcohol ethoxylates with an average EO degree of 9 to15 and, more particularly, 9 to 12.

It has proved to be useful in this regard to use the components ofsubclass (a1) in larger quantities than the corresponding emulsifiers ofsubclass (a2) for this subcombination of emulsifiers belonging to theclass (a) compounds. Components (a1) and (a2) are preferably used inmixing ratios of at least 2:1.

The average degree of ethoxylation of components (b) is distinctly lowerthan in emulsifier components (a1) and/or (a2) commensurate with theshorter chain length of the basic alcohol component in this case.Head-fractionated C₈ fatty alcohol ethoxylates with an average degree ofethoxylation of 1.5 to 2.5 are preferably used as the dispersantcomponent (b).

According to the invention, particularly suitable active-substancemixtures contain, for example, 55 to 70% by weight of emulsifiercomponent (a1) together with 20 to 30% by weight of emulsifier component(a2) in addition to small quantities of dispersant component (b). Asalready mentioned, the lower limit to the active-substance components(b) is approximately 2% by weight, based on the sum of components (a)and (b), although at least 5% by weight of component (b) is preferablypresent in the mixture of active substances.

It is a particular advantage of the degreasing preparations according tothe invention that good results can even be obtained without the use ofadditional solvents, for example in the degreasing of pelts. Inpractice, the combination of dispersants and emulsifiers has afat-dissolving and fat-dispersing effect in soaking and liming and,quite generally, in degreasing. The steps involved, for example, insoaking and liming are accelerated by the use of the degreasingpreparations according to the invention.

In another preferred embodiment, the degreasing preparations accordingto the invention may contain other special selected solvents. Although,basically, any solvents capable--by their combined action--of adequatelydissolving, emulsifying and/or dispersing the auxiliaries or rather thefats and waxes to be taken up from the skin may be used, specialselection criteria are useful and preferred for the purposes of theinvention:

Solvents in the context of the invention are, in particular,corresponding organic, water-immiscible or substantiallywater-immiscible liquids distinguished by sufficiently high flash points(usually above 100° C.). Suitable solvents liquid at room temperatureare corresponding organic components characterized by biodegradability.

Suitable biodegradable liquid phases are, quite generally, carboxylicacid esters and, in particular, esters of monobasic carboxylic acidswith monohydric alcohols, high-boiling ethers, corresponding oleophilicalcohols liquid at room temperature and/or carbonic acid esters. It canbe useful in this regard--particularly among the class of carbonic acidesters--to select representatives of unsaturated components on the sideof the ester-forming carboxylic acids and/or ester-forming alcohols. Theunsaturated ester-forming components in question are preferablycompounds liquid at room temperature, so that small quantities of theester-based auxiliary liquids remaining behind in the skin or leatherstructure do not lead to any unwanted paraffin-like deposits, even afterany subsequent saponification or partial saponification.

The quantity of biodegradable solvent used may vary within wide limitsand, for example, may make up from 5 to 95% by weight of the mixture.The mixture of components (a) and (b) preferably makes up 5 to 90% byweight of these solvent-containing preparations. Corresponding solutionscontaining 10 to 60% by weight of components (a) and (b) in abiodegradable solvent or solvent mixture are particularly suitable. Thepercentages by weight mentioned are all based on the product as a whole.

Suitable auxiliary solvents based on unsaturated esters are, inparticular, compounds of corresponding olefinically unsaturated higherfatty acids, for example oleic acid, with optionally unsaturated higherfatty alcohols, more particularly oleyl alcohol. Examples of thealcohol-based solvent phase are Guerbet alcohols, more particularly inthe range up to C₂₀. The choice of ethers and, in particular, oleophilicalcohols liquid under normal conditions can lead to improved results inregard to the hydrolysis stability of the biodegradable solvent used asthe auxiliary liquid phase.

EXAMPLES

To determine the particular degreasing effect, pickled sheepskins arecut along the spinal line. The right-hand and left-hand halves areidentified as belonging to one another, after which--in separateprocesses--one half is processed using the degreasing preparationsaccording to the invention while the other half is processed using knownstandard or comparison products from the field of degreasingpreparations. The following procedure is adopted:

Procedure for testing degreasing preparations

Starting material: pickled English domestic sheepskins

Percentages based on pickled weight

Initial pH: approximately 1.8

Cut the skins along the spinal lines. Mark right-hand and left-handhalves (at the neck). Process the right-hand half with the test productand the left-hand half with the standard or comparison product.

    __________________________________________________________________________                                 Running                                                      Product/         time in                                          Step  % by wt.                                                                            remarks      °C.                                                                        mins.                                                                              pH value                                    __________________________________________________________________________    Degreasing                                                                          6     Degreasing                                                                    preparation                                                                   Water        35                                                               so that both                                                                  together give a                                                               30% liquor                                                                    Running time     60                                               Pretanning                                                                          +3    Sodium aluminium silicate                                                     (commercial product                                                           "Coratyl G")                                                            0.3   Dicarboxylic acid                                                                              60                                                           (commercial product                                                           "Coratyl S")                                                            +2    Chrome syntan                                                                 (commercial product                                                           "Tannesco HN")                                                          0.2   Dicarboxylic acid     5                                                       (commercial product                                                           "Coratyl S")                                                            +20   Water        35  60   3.8                                               +50   Water        40  30                                                     +100  Water        40  30   4.0                                                     Drain off                                                                     liquor                                                            Washing                                                                             300   Water        40  15                                                           Drain off                                                                     liquor                                                                  300   Water        40  15                                                           Drain off                                                                     liquor                                                                  300   Water        40  15                                                           Drain off                                                                     liquor                                                                  300   Water        20  15                                               __________________________________________________________________________

Hoard up leather overnight, sammy, tenter and dry at 25° C. Cut outmaterial for fat determination at the DIN removal point and use todetermine residual fats.

Degreasing was carried out in known manner with three different knowndegreasing preparations (tests a to c) and, for comparison, with abiodegradable degreasing preparation formulated in accordance with theinvention (test d) under the same working conditions. In addition, it isclear from a comparison of example d) according to the invention withtest e) that the quantity of the head-fractionated fatty alcoholethoxylate is a critical feature.

The individual results obtained in several tests are set out in Table 1below; the natural fat content of the skins used (i.e. beforedegreasing) was 23 to 27% by weight.

                  TABLE 1                                                         ______________________________________                                                                     Residual fat                                                                  content after                                                                 degreasing                                                                    (in % by                                         No.  Degreasing preparation used                                                                           weight)                                          ______________________________________                                        a)   15% by weight                                                                             organic solvent 4.0-6.0                                                       (petroleum)                                                       1.5% by weight                                                                            NP-10                                                        b)   6% by weight                                                                              NP-10           4.0-5.0                                      c)   6% by weight                                                                              mixture of NP-10 with                                                                         3.0-4.0                                                       organic solvent                                                               (isopropyl alcohol)                                          d)   6% by weight                                                                              product mixture of 90%                                                                        2.7-3.9                                                       Dehydol-LS7 and                                                               10% C8-1EO                                                   e)   6% by weight                                                                              product mixture of 70%                                                                        4.8-5.9                                                       Dehydol-LS7 and                                                               30% C8-1EO                                                   ______________________________________                                         Abbreviations in Table 1:                                                     NP10: Adduct of 10 moles of ethylene oxide with 1 mole of nonylphenol         Dehydol LS7: Adduct of 7 moles of ethylene oxide with 1 mole of               C.sub.12/14 fatty alcohol (a product of Henkel KGaA, Dusseldorf)              C81EO: Adduct of 1 mole of ethylene oxide with 1 mole of C.sub.8 fatty        alcohol (octanol)                                                        

We claim:
 1. A process for degreasing skins, pelts, hides and leatherswhich comprises: contacting the skins, pelts, hides and leathers to bedegreased with a composition comprising(a) a C₁₂₋₁₈ fatty alcoholethoxylate containing, on average, more than 6 EO groups in themolecule; and (b) a head-fractionated fatty alcohol ethoxylatecontaining not more than 3 EO groups in the molecule, wherein,i) thefatty alcohol residues in components (a) and (b) have an iodine valuebelow 20 and ii) component (b) is present in an amount of from about 2to 25% by weight, based on the weight of (a) and (b).
 2. The process ofclaim 1, wherein (a) comprises a mixture of at least two fatty alcoholethoxylates having different average number of EO groups, with a maximumaverage of 15 EO groups.
 3. The process of claim 1 wherein component (b)comprises a head-fractionated C₈ fatty alcohol ethoxylate with anaverage number of EO groups of 1.5 to 2.5.
 4. The process of claim 1wherein component (a) comprises a mixture of,(a1) a saturated C₁₂₋₁₈fatty alcohol ethoxylate with an average of 6 to 8 EO groups and (a2) asaturated C₁₂₋₁₈ fatty alcohol ethoxylate with an average of about 9 to12 EO groups.
 5. The process of claim 1 wherein components (a) and (b)are dissolved in a biodegradable solvent, liquid at room temperature,comprising at least one member selected from the group consisting ofcarboxylic acid esters, ethers, alcohols and carbonic acid esterswherein the solvent has a flash point above 100° C.
 6. The process ofclaim 5, wherein components (a) and (b) are present in the biodegradablesolvent in an amount of 5 to 90% by weight, based on the weight of (a),(b) and the biodegradable solvent.
 7. The process of claim 5 wherein thesolvent comprises at least one member selected from the group consistingof Guerbet alcohols and higher olefinically unsaturated fatty alcohols.8. The process of claim 2 wherein the fatty alcohol ethoxylate comprisean average of up to 10 EO groups.
 9. The process of claim 4 wherein themixing ratio of component (a1) to component (a2) is not lower than 2:1.10. The process of claim 6 wherein the components (a) and (b) arepresent in the biodegradable solvent in an amount of 10 to 60 percent byweight based on the weight of (a), (b) and the biodegradable solvent.11. The process of claim 2 wherein component (b) comprises ahead-fractionated C₈ fatty alcohol ethoxylate with an average number ofEO groups of 1.5 to 2.5.
 12. The process of claim 2 wherein component(a) comprises a mixture of,(a1) a saturated C₁₂₋₁₈ fatty alcoholethoxylate with an average of 6 to 8 EO groups and (a2) a saturatedC₁₂₋₁₈ fatty alcohol ethoxylate with an average of about 9 to 12 EOgroups.
 13. The process of claim 2 wherein components (a) and (b) aredissolved in a biodegradable solvent, liquid at room temperature,comprising at least one member selected from the group consisting ofcarboxylic acid esters, ethers, alcohols and carbonic acid esterswherein the solvent has a flash point above 100° C.
 14. The process ofclaim 13 wherein components (a) and (b) are present in the biodegradablesolvent in an amount of 5 to 90% by weight, based on the weight of (a),(b) and the biodegradable solvent.
 15. The process of claim 13 whereinthe solvent comprises at least one member selected from the groupconsisting of Guerbet alcohols and higher olefinically unsaturated fattyalcohols.
 16. The process of claim 3 wherein component (a) comprises amixture of,(a1) a saturated C₁₂₋₁₈ fatty alcohol ethoxylate with anaverage of 6 to 8 EO groups and (a2) a saturated C₁₂₋₁₈ fatty alcoholethoxylate with an average of about 9 to 12 EO groups.
 17. The processof claim 3 wherein components (a) and (b) are dissolved in abiodegradable solvent liquid at room temperature comprising at least onemember selected from the group consisting of carboxylic acid esters,ethers, alcohols and carbonic acid esters wherein the solvent has aflash point above 100° C.
 18. The process of claim 17 wherein components(a) and (b) are present in the biodegradable solvent in an amount of 5to 90% by weight, based on the weight of (a), (b) and the biodegradablesolvent.
 19. The process of claim 17 wherein the solvent comprises atleast one member selected from the group consisting of Guerbet alcoholsand higher olefinically unsaturated fatty alcohols.
 20. The process ofclaim 4 wherein components (a) and (b) are dissolved in a biodegradablesolvent, liquid at room temperature, comprising at least one memberselected from the group consisting of carboxylic acid esters, ethers,alcohols and carbonic acid esters wherein the solvent has a flash pointabove 100° C.
 21. A degreasing composition for the degreasing of skins,pelts, hides and leathers comprising a mixture of(a) C₁₂₋₁₈ fattyalcohol ethoxylate containing an average of more than 6 EO groups in themolecule; and (b) a head-fractionated fatty alcohol ethoxylatecontaining an average of not more than 3 EO groups in the molecule;wherein,i) the fatty alcohol residues in components (a) and (b) have aniodine value below 20 and ii) component (b) is present in an amount ofabout 2 to 25% by weight, based on the weight of (a) and (b); whereiniii) component (b) comprises a head-fractionated C₈ fatty alcoholethoxylate with an average number of EO groups of 1.5 to 2.5 andoptionally iv) (a) comprises a mixture of (a1) a saturated C₁₂₋₁₈ fattyalcohol ethoxylate with an average of 6 to 8 EO groups, and (a2) asaturated C₁₂₋₁₈ fatty alcohol ethoxylate with an average of about 9 to12 EO groups, the mixing ratio between components (a1) and (a2) beingnot less than 2:1, and optionally v) components (a) and (b) comprise asolution in a biodegradable solvent, liquid at room temperature,selected from the group consisting of carboxylic acid esters, ethers,alcohols and carbonic acid esters having a flash point above 100°C.,components (a) and (b) being present in an amount of 5 to 90% byweight, based on the weight of (a) and (b) and the biodegradablesolvent.